Wilhelm married three times, having the following children:
• Princess Caroline of Bavaria (1792–1873), daughter of King Maximilian I of Bavaria (1756–1825) and Princess Augusta Wilhelmina of Hesse-Darmstadt (1765–1796). They divorced in 1814.
• Catherine Pavlovna of Russia (1788–1819), daughter of Tsar Paul I of Russia (1754–1801) and Princess Sophie Dorothea of Württemberg (1759–1828). With Catherine, he had two daughters:
— Marie (1816–1887), married Count Alfred von Neipperg (1807–1865)
— Sophie (1818–1877), married King William III of the Netherlands (1817–1890)
• Pauline Therese of Württemberg (1800–1873), daughter of Duke Louis of Württemberg (1756–1817) and Princess Henrietta of Nassau-Weilburg (1780–1857). They had three children:
— Catherine (1821–1898) whom by her husband Prince Frederick of Württemberg (1808–1870) was mother to King William II of Württemberg
— Karl (1823–1891) who succeeded as King of Württemberg
— Augusta (1826–1898) who married Prince Hermann of Saxe-Weimar-Eisenach (1825–1901); one of their daughters, Pauline of Saxe-Weimar-Eisenach married Charles Augustus, Hereditary Grand Duke of Saxe-Weimar-Eisenach.